EC - Cysteine-S-conjugate β-lyase

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IntEnz Enzyme Nomenclature


Accepted name:
cysteine-S-conjugate β-lyase
Other names:
cysteine conjugate β-lyase
glutamine transaminase K/cysteine conjugate β-lyase
L-cysteine-S-conjugate thiol-lyase (deaminating)
cystathionine β-lyase
cystine lyase
cystathionine L-homocysteine-lyase (deaminating)
L-cystathionine L-homocysteine-lyase (deaminating)
S-alkylcysteine lyase
alkylcysteine lyase
S-alkyl-L-cysteine sulfoxide lyase
S-alkyl-L-cysteine lyase
alkyl cysteine lyase
S-alkyl-L-cysteine alkylthiol-lyase (deaminating)
Systematic name:
L-cysteine-S-conjugate thiol-lyase (deaminating; 2-aminoprop-2-enoate-forming)




A pyridoxal 5'-phosphate protein. The enzyme is promiscuous regarding the moiety conjugated to L-cysteine, and can accept both aliphatic and aromatic substitutions. The enzyme cleaves a carbon-sulfur bond, releasing a thiol and an unstable enamine product that tautomerizes to an imine form, which undergoes a hydrolytic deamination to form pyruvate and ammonia. While bacteria and plants have dedicated enzymes, all of the animal enzymes discovered thus far are bifunctional, most of which also act as aminotransferases. Formerly EC and EC

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0047804
CAS Registry Number: 68652-57-3
UniProtKB/Swiss-Prot: (34) [show] [UniProt]


  1. Tateishi, M., Suzuki, S. and Shimizu, H.
    Cysteine conjugate β-lyase in rat liver. A novel enzyme catalyzing formation of thiol-containing metabolites of drugs.
    J. Biol. Chem. 253: 8854-8859 (1978). [PMID: 721818]
  2. Stevens, J. L.
    Isolation and characterization of a rat liver enzyme with both cysteine conjugate beta-lyase and kynureninase activity.
    J. Biol. Chem. 260: 7945-7950 (1985). [PMID: 4008484]
  3. Stevens, J. L., Robbins, J. D., Byrd, R. A.
    A purified cysteine conjugate beta-lyase from rat kidney cytosol. Requirement for an alpha-keto acid or an amino acid oxidase for activity and identity with soluble glutamine transaminase K.
    J. Biol. Chem. 261: 15529-15537 (1986). [PMID: 3782077]
  4. Gaskin, P. J., Adcock, H. J., Buckberry, L. D., Teesdale-Spittle, P. H., Shaw, P. N.
    The C-S lysis of L-cysteine conjugates by aspartate and alanine aminotransferase enzymes.
    Hum Exp Toxicol 14: 422-427 (1995). [PMID: 7612304]
  5. Cooper, A. J., Bruschi, S. A., Iriarte, A., Martinez-Carrion, M.
    Mitochondrial aspartate aminotransferase catalyses cysteine S-conjugate beta-lyase reactions.
    Biochem. J. 368: 253-261 (2002). [PMID: 12137566]
  6. Cooper, A. J., Bruschi, S. A., Conway, M., Hutson, S. M.
    Human mitochondrial and cytosolic branched-chain aminotransferases are cysteine S-conjugate beta-lyases, but turnover leads to inactivation.
    Biochem. Pharmacol. 65: 181-192 (2003). [PMID: 12504794]
  7. Cooper, A. J., Pinto, J. T.
    Cysteine S-conjugate beta-lyases.
    Amino Acids 30: 1-15 (2006). [PMID: 16463021]
  8. Flavin, M. and Slaughter, C.
    Cystathionine cleavage enzymes of Neurospora.
    J. Biol. Chem. 239: 2212-2219 (1964). [PMID: 14209950]
  9. Natsch, A., Schmid, J., Flachsmann, F.
    Identification of odoriferous sulfanylalkanols in human axilla secretions and their formation through cleavage of cysteine precursors by a C-S lyase isolated from axilla bacteria.
    Chem. Biodivers. 1: 1058-1072 (2004). [PMID: 17191898]

[EC created 1981, modified 2018 (EC created 1965, deleted 1972, reinstated 1976, incorporated 2018) (EC created 1972, incorporated 2018)]